Tripod joints, which are also referred to as “constant velocity universal joints” (abbreviated CV joints) or also as “homokinetic joints” have long been known from the prior art. For example, they are used as internal joints for the drive shafts of front-wheel driven motor vehicles. They exhibit excellent constant-velocity properties and can be bent to angles of typically more than 10°. Furthermore, tripod joints can advantageously also be used for cardan shafts of rear-wheel driven or four-wheel driven motor vehicles. However conventional tripod joints are problematic if the shafts are bent in an articulated manner relative to one another, i.e. if they form a working angle. Particularly in such a case it is important to avoid a relative sliding regarding the components that are in a rolling or roller contact. On the one hand, the friction resistance accompanying this sliding leads to increased wear and increased power dissipation of the joint and, on the other hand, harbors the risk of the joint shaking. This not only reduces the life of the bearings of the shafts interconnected by the joints, but also affects the running smoothness of the vehicle.
Great efforts are being made to improve the running characteristics of tripod joints. For example, DE 41 301 83 A1 discloses a tripod joint in which a tilting of the outer ring in the track, e.g. in the case of a load introduction or change of a load, is supposed to be avoided by means of a special design of the tracks in the outer joint member and of the outer rings of the rollers. This rolling contact between the roller and the track of the outer joint member is not the subject matter of the present invention.
Other issues which are the subject matter of the present invention are the rolling contacts between the axle journal, hereinafter also referred to in short as journal, of the inner joint portion and the roller as well as the roller contacts of the components of the roller, which is usually configured as a roller bearing with an inner ring, an outer ring and several rolling elements.
For example, DE 102 06 733 A1 proposes a spherical-to-spherical contact surface between the journal and the roller, or the inner ring thereof, since it was assumed that the friction and thus the shaking would be reduced by a distribution of the Hertzian stress over as large a contact surface as possible. Surprisingly, however, the inventors of the present invention have found that the shaking increases due to this measure, i.e., that the vibration-inducing forces appear to increase.